YY Mensae

YY Mensae

A light curve for YY Mensae, plotted from Hipparcos data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Mensa
Right ascension 04h 58m 17.93697s[2]
Declination −75° 16′ 37.9879″[2]
Apparent magnitude (V) 8.60 - 8.89[3]
Characteristics
Spectral type K1 III/IVe[4]
U−B color index +0.70[5]
B−V color index +1.04[5]
Variable type FK Com[3]
Astrometry
Radial velocity (Rv)−8.5±2.5[6] km/s
Proper motion (μ) RA: −4.149 mas/yr[2]
Dec.: −3.077 mas/yr[2]
Parallax (π)4.5587 ± 0.0161 mas[2]
Distance715 ± 3 ly
(219.4 ± 0.8 pc)
Absolute magnitude (MV)+0.81[7]
Details
Mass0.983[8] M☉
Radius12.3[9] R☉
Luminosity68.5[10] L☉
Surface gravity (log g)1.63[11] cgs
Temperature4,691±128[12] K
Metallicity [Fe/H]−0.59[11] dex
Rotational velocity (v sin i)45±2[13] km/s
Other designations
YY Men, CD−75°189, CPD−75°292, HD 32918, HIP 23106[14]
Database references
SIMBADdata

YY Mensae, also known as HD 32918, is a variable star located in the southern circumpolar constellation Mensa. It has an apparent magnitude that fluctuates between 8.6 and 8.9,[3] which is within the visibility of binoculars. Based on parallax measurements from Gaia DR3, it is estimated to be 715 light years distant.[2] It appears to be approaching the Solar System with a heliocentric radial velocity of −8.5 km/s.[6]

This star was known to have an unusual spectrum since the 1970's, but its variability wasn't observed until the 1980's. Collier (1982) found it to be a FK Comae Berenices variable, a class of rapidly rotating giant stars.[15] After a few additional years of observations, HD 32918 was given the variable star designation YY Mensae.[16] A paper in 1987 observed a long and powerful flare coming from the star.[17] X-ray emissions from YY Mensa have been detected in its corona, which may be a result of its fast rotation.[18]

YY Mensae has a stellar classification of K1 III/IVe,[4] indicating an evolved red giant with the blended luminosity class of a giant star and a subgiant. It is chromospherically active and emission lines are also present in its spectra. It has 98% the mass of the Sun[8] but has expanded to 12.3 times its girth.[9] It radiates 68.5 times the luminosity of the Sun[10] from its photosphere at an effective temperature of 4,691 K,[12] giving it an orange hue. Typical for stars its type, YY Mensae spins rapidly, having a projected rotational velocity of 45 km/s.[13] The star is metal deficient, having an iron abundance only 26% that of the Sun.[11]

  1. ^ Cite error: The named reference HIPCurve was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Bidelman1973 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Cutispoto2001 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Anders2022 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Strassmeier2009 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference McDonald2012 was invoked but never defined (see the help page).
  11. ^ a b c Cite error: The named reference Sprague2022 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Stassun2019 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Fekel1993 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Collier1982 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Kholopov1985 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Slee1981 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Audard2004 was invoked but never defined (see the help page).